Conventionally, flame retardant styrene-based resins have fabricability, a good balance of mechanical properties, and excellent electric insulation, and therefore they are used in wider fields such as electrical and electronic equipment and OA equipment. On the other hand, recently, a trend toward suppression in discharge of volatile organic compounds (Volatile Organic Compounds: VOC) has promoted use of non-coated resins for housings used in the fields of electrical and electronic equipment and OA equipment. For this reason, there has been a desire for resins that have high designability that can address various color tones, for example, can be colored in a vivid color or a deep color. It has previously been reported that a transparent flame retardant resin composition has high coloring physical properties and designability in which a phosphoric acid ester-based flame retardant is compounded with a rubber-reinforced styrene-based resin obtained by copolymerization of an unsaturated carboxylic acid alkyl ester (for example, see Patent Literatures 1 to 5). A transparent rubber-reinforced styrene-based resin obtained by copolymerization of an unsaturated carboxylic acid alkyl ester is used as a base resin, thus obtained transparent flame retardant resin composition has high coloring properties and designability. Because the unsaturated carboxylic acid alkyl ester is compounded, however, stability of the flame retardancy and the mechanical properties, particularly the falling dart impact resistance, weld strength, and Charpy impact strength are insufficient, and further improvement thereof has been desired. Moreover, a resin composition comprising a rubber containing graft copolymer, a copolymer consisting of a monomer mixture containing a methyl methacrylate monomer, and a flame retardant compounded with these has been reported (for example, see Patent Literature 6). The styrene-based resin disclosed in Patent Literature 6 demonstrates an effect in the flame retardancy, designability, and scratch resistance, but stability of the flame retardancy and mechanical properties, particularly the falling dart impact resistance, weld strength, Charpy impact strength, and the like are inferior. Additionally, the electrical and electronic equipment using this styrene-based resin and the like do not show satisfactory results in a product drop practical test. Accordingly, further improvement has been desired. Meanwhile, a resin composition in which scratch resistance, designability, and impact resistance are improved, and no flame retardant is compounded has been reported (for example, see Patent Literature 7). Unfortunately, the falling dart impact resistance, weld strength, and the like of this resin composition do not show satisfactory results in the product drop practical test, and therefore further improvement has been desired.